1. Field of the Invention
Embodiments of the present disclosure relate generally to an analog to digital conversion, and, in particular, to an analog to digital converter that provides a direct (D) and quadrature (Q) output.
2. Description of the Related Art
Analog to digital converters (ADCs) are widely employed within circuits for a variety of technologies. Depending upon the application, different types of ADC converters having different properties may be used. FIG. 1 is a functional block diagram of a delta ADC 100, one type of ADC that is well known in the art. The delta ADC 100 comprises a comparator 102, an integrator 104, and a digital to analog converter (DAC) 106. An input signal is coupled to the non-inverting input of the comparator 102, with the output of the comparator 102 coupled to the integrator 104. The output from the integrator 104 is coupled to the DAC 106, and the output of the DAC 106 feeds back into the inverting input of the comparator 102.
The integrator 104 integrates up or down and has an output coupled to the DAC 106. The output from the DAC 106 is then compared to the input signal by the comparator 102. Consequently, the DAC 106 ramps up or down at a limited rate until its output becomes equal to the input signal, at which time it essentially follows the input signal.
ADCs such as the delta ADC 100 are employed in circuits for many applications, such as communications, that require both real (or direct) and quadrature signal components. A great deal of effort may be required to create both the direct and quadrature signal components following the analog to digital conversion, requiring additional complexity in the circuit.
Therefore, there is a need in the art for an analog to digital converter that provides both a direct and a quadrature output.